System of fluid cooled fuses

ABSTRACT

A system of fluid cooled electric fuses is made up of a modular stack of alternating fuse units, and cooling units, or heat exchangers, which are cooled by transverse flows of a cooling medium which flows through said cooling units, or heat exchangers.

United States Patent Kozacka [4 1 June 20, 1972 [54] SYSTEM OF FLUID COOLED FUSES [72] Inventor: Frederick J. Kozacka, South Hampton,

[73] Assignee: The Chase-Shawmut Company, Newburyport, Mass.

[22] Filed: Dec. 10, 1970 [21] Appl. No.: 96,761

[52] US. Cl ...337/166, 337/222, 337/292 [51] Int. Cl. ..H01h 85/04 [58] Field ofSearch ..337/l58,l61,163, 166,182,

[56] References Cited UNITED STATES PATENTS 3,453,579 1/1969 Cinquin ..337/161X 3,562,691 2/1971 Cinquin ..337/16l X 2,809,254 10/1957 Edsall 2,871,314 1/1959 Swain et a1 ..337/158 X FOREIGN PATENTS OR APPLICATIONS 694,140 11/1930 France ..337/292 Primary Examiner-Bernard A. Gilheany Assistant E .\-aminer-Dewitt M. Morgan Attorney-Erwin Salzer [57] ABSTRACT A system of fluid cooled electric fuses is made up of a modular stack of alternating fuse units, and cooling units, or heat exchangers, which are cooled by transverse flows of a cooling medium which flows through said cooling units, or heat exchangers.

7 Claims, 3 Drawing Figures I I'IIIIIII'IIII PATENTEnJuwzo 1272 3,671.91 1

":1 J a 'IIIIIIIIIII SYSTEM or FLUID coouzn FUSES BACKGROUND OF INVENTION The amounts of heat generated in some electric fuses make it necessary to provide such fuses with cooling means, or heat exchangers, based on heat convection. A relatively .early design of fuse structures cooled by convection is shown in US. Pat. No. 2,871,3l4to K.W. Swain et al., Jan. 27, 1959 for COMPOSITE CURRENT LIMITING FUSESTRUCTURES. Convection cooling as shown in the above patent .was not sufficiently effective for the requirements of a numberof applications, and it became necessary to provide fuse structures with effective means forforced convection cooling, in particular with means for forced cooling by a cooling liquid such as water. Most electric fuses are provided with fuse links having serially arranged points of reduced cross-sectional area to form series breaks upon occurrence of major fault currents. It is difficult to cool efiectively fuses which are provided with such fuse .links,. Considering a fuse structure which is surrounded by a water jacket, the pulverulent arc-quenching filler of the fuse which is interposed between itsfuselinks and the cooling medium tends to severely limit the cooling effectiveness of such an arrangement. All arc-quenching fillers have a much smaller thermal conductivity than high heat conductivity metals as, for instance, copper, and the air'filled interstices between the granules of an arc-quenching filler greatly decreases its thermal conductivity. Surrounding afuse with a water jacket further means interposing the walls bounding the water jacket between the arc-quenching filler and the water inside of the water jacket. These walls cannotbe made of a relatively good conductor of heat such as copper, but must be made of a relatively bad conductor of'heat such as, for instance, a ceramic material. These factors make it understandable that the cooling effectiveness of outer water jackets, or like cooling means, is insufficient where relatively large amounts ofheat must be removed from a fuse structure.

This invention refers to a composite fuse and heat exchanger structure intended and adapted forforced cooling whose cooling efficiency far surpasses any prior art fuse cooling structure.

SUMMARY OF INVENTION A system of fluid cooled fuses embodying this invention includes a plurality of substantially tubular fuse units each closed by a pair of terminal elements, and a plurality of cooling units each having a surface abutting against the surface of one of said terminal elements, said fuse units and said cooling units being superimposed in alternating fashion and jointly forming a composite stack structure. Each of said cooling units defines a fluid passageway substantially at right angles to the axis of said fuse units.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an exploded view of a composite stack embodying this invention including fuse units alternating with cooling units, the fuse units being shown in vertical section, and the cooling units in side elevation, FIG. 1 further showing one portion of one of the cooling units as being broken away;

FIG. 2 shows an assembled composite stack embodying this invention substantially in the same fashion as FIG. 1; and

FIG. 3 is a top-plan view of a cooling unit, or heat exchanger, as shown in FIGS. 1 and 2.

DESCRIPTION OF PREFERRED EMBODIMENT 1n the drawings reference character F has been applied to generally designate substantially tubular fuse units, and reference character C has been applied to designate substantially cylindrical self-contained cooling units, or heat exchangers. Each fuse unit F includes a tubular casing of insulating material 1, a pair of terminal elements or internal terminal plugs 2 closing the ends of casing l, a body of quartz sand 3 inside of casing l, and a silver ribbon fuse link 4 inside casing l conductively'interconnecting terminal plugs 2, and immersed in the body of quartz sand 3. Steel pins 5 projecting transversely through casing 1 into tenninal plugs 2 firmly secure terminal plugs 2 to casing l. Ribbon fuse link 4 has a single point 4 of reduced cross-sectional area which forms a point-heat source when the fuse link is carrying current. The point 4 of reduced cross-sectional area is formed by a pair of lateral, sub stantially V-shaped incisions. This type of fuselink is indicated for best results, i.e., the type of fuse link having but one single point of reduced cross-sectional area between terminal elements 2 is indicated. While it is very desirable that each fuse link 4 is provided with but one single point of reduced crosssectional area rather than serially related points of reduced cross-sectional area, several fuse links 4 may be arranged in each casing l, and connected in parallel to increase the current-carrying capacity of the structure. Reference character 2' has been applied to indicate the axially outer planar end surfaces of terminal plugs 2. Each cooling unit, or heat exchanger C is substantially inthe shape of a cylinder, i.e., it has a cylindrical lateral surface and a pair of planar circular end surfaces .6. The end surfaces 6 .ofheat exchangers C abut against the axially outer end surfaces 2' of terminal plugs 2, and are clamped by screw means into firm engagement with end surfaces 2'. To this endeach terminal plug 2 is provided in the center thereof with an internally screw-threaded recess or bore 2", and each heat exchanger C is provided in the center thereof with an externally screw-threaded projection 7 adapted to enter into the screw-threaded recesses 2"-of terminal plugs 2. Each heat exchanger, or cooling unit C defines a laterally closed tunnel-like passageway 8 arranged at right angles to the axis thereof. Each heat exchanger C has a pair of fluid connectors 9 projecting radially outwardly from the cylindrical surface thereof. The arrows of FIG. 2 indicate the flow of cooling fluid into heat exchangers C and out of heat exchangers C. It will be noted that the diameter of terminal plugs 2 and the diameter of the heat exchangers C is substantially equal to maximize the heat flow away from the former to the latter.

To provide each fuse unit F with a fuse link 4 having but one single point of reduced cross-sectional area 4 minimizes heat generation within each fuse unit F. A single break fuse is generally capable of controlling circuits up to a circuit voltage of volts. Higher circuit voltages require series arrangements of fuses and interposition of a heat exchanger, or cooling unit C between each pair of fuse units F. The composite modular fuse unit and cooling unit structure shown in the drawings includes two fuse units F, and three cooling units C, and is intended for circuits having a circuit voltage up to 250 volts. Circuit voltages above 250 volts up to 390 volts call for a series arrangement of three fuse units F, and circuit voltages above 390 volts up to about 520 volts call for stacks including four serially arranged fuse units F. Because-of the modular character of the system it is easy to form a composite stack which lives up to any requirement which may occur in any given installation. It will be apparent from FIGS. 1 and 2 that in a stack structure embodying this invention the number of cooling or heat exchanges C exceeds by one the number of fuse units F.

The cooling units, or heat exchangers C are made of metal having a high heat conductivity, e.g., copper.

The flow of cooling medium through cooling units C is effected by a pump (not shown).

I claim as my invention:

1. A system of fluid cooled fuses including a plurality of substantially tubular fuse units each closed on the ends thereof by a pair of internal terminal plugs, said system further including a plurality of selfcontained metallic cooling units having planar surfaces adapted to abut against the axially outer end surfaces of said terminal plugs of said plurality of fuse units and clamped by screw means against said surfaces, said plurality of fuse units being arranged in coaxial relation and axially spaced from each other, and at least one of said plurality of said cooling units being arranged between one spaced pair of said plurality of fuse units and jointly defining with said spaced pair a composite stack structure terminated on each of the axially outer ends thereof by one of said plurality of cooling units, and each of said plurality of cooling units defining a laterally closed tunnel-like fluid passageway extending substantially at right angles to the axis of said stack structure.

2. A system as specified in claim 1 wherein each of said plurality of cooling units is substantially cylindrical and provided with axially extending externally screw-threaded projections on opposite end surfaces thereof entering into internally screw-threaded bores provided in said pair of terminal plugs of said plurality of fuse units.

3. A system as specified in claim 2 wherein the diameter of said pair of terminal plugs of said plurality of fuse units and the diameter of said plurality of cooling units is substantially equal, and wherein each of said plurality of cooling units is provided with a pair of fluid connectors projecting radially outwardly beyond the cylindrical lateral surface thereof.

4. The combination of a. a pair of electric fuses each including a tubular casing of insulating material, a pair of internal terminal plugs closing the ends of said casing and having axially outer planar end surfaces, a body of quartz sand inside said casing and a ribbon fuse link inside said casing conductively interconnecting said pair of terminal plugs and immersed in said body of quartz sand, and said pair of terminal plugs having internally screw-threaded bores in the centers thereof; and

b. three substantially cylindrical heat exchangers of metal having circular planar end surfaces adapted to abut against said axially outer planar end surfaces of said pair of terminal plugs of said pair of fuses, said planar end surfaces of said heat exchangers having externally screwthreaded projections in the centers thereof adapted to extend into said screw-threaded bores of said terminal plugs of said pair of fuses, said pair of fuses and said heat exchangers being superimposed to form a stack, one of said heat exchangers being arranged between said pair of fuses and the other said heat-exchangers forming the ends of said stack, each of said heat-exchangers defining a laterally closed tunnel-like passageway for cooling fluid arranged at right angles to the axis of each of said heat exchangers, and each of said heat exchangers having a pair of fluid connectors projecting radially outwardly from the cylindrical surface thereof.

5. In a composite fuse structure and cooling structure the combination of a. a plurality of coaxially arranged axially spaced fuse units each including a tubular casing, a pair of internal terminal plugs inserted into and closing the ends thereof and ribbon fuse link means conductively interconnecting said pair of terminal plugs, said ribbon fuse link means having but one single point of reduced cross-sectional area between the axially inner end surfaces of said pair of terminal plugs;

b. a plurality of cooling units each having a planar heat exchange surface adapted to be arranged in abutting relation to the axially outer end surfaces of said terminal plugs of said plurality of fuse units, each of said plurality of cooling units having a laterally closed tunnel-like fluid passageway extending substantially at right angles to the axis of said plurality of fuse units and one of said plurality of cooling units being arranged to each side of said one single point of reduced cross-sectional area of said fuse link means of each of said plurality of fuse units; and

. clamping means clamping said plurality of fuse units and said plurality of cooling units into an integral stack structure and exerting pressure between one of said axially outer end surfaces of said pair of terminal plugs of each of said plurality of fuse units and said heat exchange surface of one of said plurality of cooling units.

6. A composite fuse structure and fuse cooling structure forming a stack of substantially cylindrical coaxial altematin fuse units and cooling units, said stack including a plurality 0% fuse units and a plurality of cooling units, the number of said cooling units exceeding by one the number of said fuse units and at least one of said plurality of cooling units being arranged between a pair of fuse units forming part of said plurality of fuse units;

each of said plurality of fuse units including a tubular casing of electric insulating material, a pair of terminal plugs closing the ends of said casing and having an axially outer planar end surface, a body of quartz sand inside said casing and a fusible element inside said casing conductively interconnecting said pair of terminal plugs and immersed in said body of quartz sand; and each of said plurality of cooling units having a pair of planar end surfaces, at least one of said pair of end surfaces abutting under pressure against said axially outer end surface of one of said pair of terminal plugs of one of said plurality of fuse units, each of said plurality of cooling units defining a laterally closed tunnel-like passageway for cooling fluid arranged between said planar end surfaces thereof and at right angles to the axis of said stack, and each of said plurality of cooling units having a pair of fluid connectors projecting radially outwardly beyond said pair of planar end surfaces thereof. 7. A composite fuse structure as specified in claim 6 wherein a. said fusible element of each of said plurality of fuse units is a ribbon fuse link provided with one single point of reduced cross-sectional area between said pair of terminal plugs thereof; said pair of terminal plugs of each of said plurality of fuse units is provided with an internally screw-threaded bore arranged in coaxial relation with said axis of said stack; and c. each of said pair of planar end surfaces of each of said plurality of cooling units is provided with a stud projection arranged in coaxial relation with the axis of said stack and having an external screw-thread matching said internally screw-threaded bore in each of said pair of terminal plugs of each of said plurality of fuse units. 

1. A system of fluid cooled fuses including a plurality of substantially tubular fuse units each closed on the ends thereof by a pair of internal terminal plugs, said system further including a plurality of self-contained metallic cooling units having planar surfaces adapted to abut against the axially outer end surfaces of said terminal plugs of said plurality of fuse units and clamped by screw means against said surfaces, said plurality of fuse units being arranged in coaxial relation and axially spaced from each other, and at least one of said plurality of said cooling units being arranged between one spaced pair of said plurality of fuse units and jointly defining with said spaced pair a composite stack structure terminated on each of the axially outer ends thereof by one of said plurality of cooling units, and each of said plurality of cooling units defining a laterally closed tunnel-like fluid passageway extending substantially at right angles to the axis of said stack structure.
 2. A system as specified in claim 1 wherein each of said plurality of cooling units is substantially cylindrical and provided with axially extending externally screw-threaded projections on opposite end surfaces thereof entering into internally screw-threaded bores provided in said pair of terminal plugs of said plurality of fuse units.
 3. A system as specified in claim 2 wherein the diameter of said pair of terminal plugs of said plurality of fuse units and the diameter of said plurality of cooling units is substantially equal, and wherein each of said plurality of cooling units is provided with a pair of fluid connectors projecting radially outwardly beyond the cylindrical lateral surface thereof.
 4. The combination of a. a pair of electric fuses each including a tubular casing of insulating material, a pair of internal terminal plugs closing the ends of said casing and having axially outer planar end surfaces, a body of quartz sand inside said casing and a ribbon fuse link inside said casing conductively interconnecting said pair of terminal plugs and immersed in said body of quartz sand, and said pair of terminal plugs having internally screw-threaded bores in the centers thereof; and b. three substantially cylindrical heat exchangers of metal having circular planar end surfaces adapted to abut against said axially outer planar end surfaces of said pair of terminal plugs of said pair of fuses, said planar end surfaces of said heat exchangers having externally screw-threaded projections in the centers thereof adapted to extend into said screw-threaded bores of said terminal plugs of said pair of fuses, said pair of fuses and said heat exchangers being superimposed to form a stack, one of said heat exchangers being arranged between said pair of fuses and the other said heat-exchangers forming the ends of said stack, each of said heat-exchangers defining a laterally closed tunnel-like passageway for cooling fluid arranged at right angles to the axis of each of said heat exchangers, and each of said heat exchangers having a pair of fluid connectors projecting radially outwardly from the cylindrical surface thereof.
 5. In a composite fuse structure and cooling structure the combination of a. a plurality of coaxially arranged axially spaced fuse units each including a tubular casing, a pair of internal terminal plugs inserted into and closing the ends thereof and ribbon fuse link means conductively interconnecting said pair of terminal plugs, said ribbon fuse link means having but one single point of reduced cross-sectional area between the axially inner end surfaces of said pair of terminal plugs; b. a plurality of cooling units each having a planar heat exchange surface adapted to be arranged in abutting relation to the axially outer end surfaces of said terminal plugs of said plurality of fuse units, each of said plurality of cooling units having a laterally closed tunnel-like fluid passageway extending substantially at right angles to the axis of said plurality of fuse units and one of said plurality of cooling units being arranged to each side of said one single point of reduced cross-sectional area of said fuse link means of each of said plurality of fuse units; and c. clamping means clamping said plurality of fuse units and said plurality of cooling units into an integral stack structure and exerting pressure between one of said axially outer end surfaces of said pair of terminal plugs of each of said plurality of fuse units and said heat exchange surface of one of said plurality of cooling units.
 6. A composite fuse structure and fuse cooling structure forming a stack of substantially cylindrical coaxial alternating fuse units and cooling units, said stack including a plurality of fuse units and a plurality of cooling units, the number of said cooling units exceeding by one the number of said fuse units and at least one of said plurality of cooling units being arranged between a pair of fuse units forming part of said plurality of fuse units; each of said plurality of fuse units including a tubular casing of electric insulating material, a pair of terminal plugs closing the ends of said casing and having an axially outer planar end surface, a body of quartz sand inside said casing and a fusible element inside said casing conductively interconnecting said pair of terminal plugs and immersed in said body of quartz sand; and each of said plurality of cooling units having a pair of planar end surfaces, at least one of said pair of end surfaces abutting under pressure against said axially outer end surface of one of said pair of terminal plugs of one of said plurality of fuse units, each of said plurality of cooling units defining a laterally closed tunnel-like passageway for cooling fluid arranged between said planar end surfaces thereof and at right angles to the axis of said stack, and each of said plurality of cooling units having a pair of fluid connectors projecting radially outwardly beyond said pair of planar end surfaces thereof.
 7. A composite fuse structure as specified in claim 6 wherein a. said fusible element of each of said plurality of fuse units is a ribbon fuse link provided with one single point of reduced cross-sectional area between said pair of terminal plugs thereof; b. said pair of terminal plugs of each of said plurality of fuse units is provided with an internally screw-threaded bore arranged in coaxial relation with said axis of said stack; and c. each of said pair of planar end surfaces of each of said plurality of cooling units is provided with a stud projection arranged in coaxial relation with the axis of said stack and having an external screw-thread matching said internally screw-threaded bore in each of said pair of terminal plugs of each of said plurality of fuse units. 